Entropy is a measure of the amount of disorder found in a system. The more disorder that is present in a system, the more stable it tends to be, such as when a bag of marbles falls on the floor and they spread all over the place.


This indicates that gases, with no fixed shape or volume, would be the most disordered, whilst solids, with a fixed shape and volume, would be the least.

Examples of increase in entropy:

  • Change of state from solid to liquid, liquid to gas
  • Reactions were gas molecules are created
  • Increase in temperature (whilst not changing state)

H20(l) –> H20(g)

2NH4NO3(s) + Ba(OH)(2).8H2O(s) –> Ba(NO3)(aq) + 2NH3(g) + 10H2O(l)

Another reaction that increases the entropy is that of diamonds changing in graphites.

Diamond(S) –> Graphite(s)